Barcelona - 30 September 2018: Six people were arrested in Barcelona on Saturday after pro-independence protesters clashed with riot police, and as thousands joined rival demonstrations to mark the first anniversary of Catalonia's polarising vote on secession.

A group of masked pro-separatists held back by riot police pelted them with eggs and hurled powder paint, creating dark clouds of dust in streets that would usually be thronged with tourists. Scuffles also broke out later in the day with police using their batons to contain the fighting.

Over several hours pro-independence groups chanting "No forgetting, no forgiveness" faced off with unionist protesters shouting, "Long live Spain".

Fourteen people received treatment for minor injuries received in the protests, local press reported.

Tensions remain high in the independence-minded region a year after the October 1 referendum deemed illegal by Madrid but celebrated by separatist Catalans.

Voters chose overwhelmingly to become independent, though turnout was low with those against secession largely boycotting the vote.

According to Catalan authorities almost 1000 people were injured last year after police tried to stop the vote going ahead at polling stations across the region in violent clashes.

Pro-independence groups had camped out overnight on Friday to prevent a demonstration in support of the national police. The demonstration went ahead but was forced to take a different route.

Narcis Termes, 68, an electrician attending the separatist protest with his wife said he was no longer hopeful about the prospects of Catalonia gaining independence.

"Last year we lived through one of our best moments. I watched my parents cry with joy at being able to vote but now we are stuck," he said.

Despite managing a vital if narrow victory in regional elections last December, Catalan pro-independence parties have struggled to retain momentum this year with many of their best known leaders either in self imposed exile or in detention awaiting trial for their role in organising the referendum and subsequent declaration of independence.

Joan Puig, a 42-year-old mechanic recording the protest in support of the police on his phone, said the conflict had been stoked by politicians on both sides. "It’s getting more and more tense," he said.

On Saturday, Oriol Junqueras, one of nine Catalan leaders in pre-trial jail since late last year, announced he would run in European Parliament elections next year.

"Standing as a candidate for the European elections is the best way to denounce the regression in democratic values and repression we have seen from the Spanish government," he said.